In industrial fields associated with a semiconductor device, a flat panel display, a nano-bio, a nano-imprint, thin film optics, and the like, that have been rapidly developed, importance of a technology capable of non-destructively and contactlessly measuring and evaluating physical properties such as a thicknesses of a thin film of nano samples, a shape of a nano pattern, and the like, in a manufacturing process step has gradually increased.
Various multi-channel rotating-element spectroscopic ellipsometers (RE-SEs) have excellent measurement abilities like high-precision, real-time, non-destructive, and contactless schemes, and as a result have been widely used in a semiconductor manufacturing process. With the development of semiconductor device process technologies, the thickness of the thin film used for these technologies is getting smaller and smaller and thus reaches a level of atomic layer and the shape of the nano pattern is changed from a two-dimensional structure into a three-dimensional structure and thus is becoming increasingly complicated. Therefore, for the rotating-element spectroscopic ellipsometer to be continuously used as a measurement tool for next-generation semiconductor industries, it is important to continuously enhance measurement uncertainty.
There are currently no methods generally accepted to assess measurement uncertainty for an RE-SE. In 2004, Aspnes derives a theoretical equation on assessing the measurement uncertainty for the RE-SEs using a non-integral photodetector. However, the derived theoretical equation may not be applied for assessing uncertainty for state-of-the-art multi-channel RE-SEs which have been widely used in the semiconductor industries. The reason is that the state-of-the-art multi-channel RE-SEs use an integral photodetector like a CCD array for real-time measurement. Recently, the research paper published by Johs and Herzinger proves that it is practically impossible to produce a standard sample having micro defects which may not be analyzed even with the measurement precision of the state-of-the-art multi-channel RE-SEs. Therefore, a new method for quantifying measurement uncertainty which does not depend on a measurement sample has been proposed. However, the method for quantifying measurement uncertainty essentially requires measurement values of several incident angles. However, the RE-SEs used in the semiconductor industries use the fixed incident angle and therefore the method for assessing measurement uncertainty thereof has not widely been used. For another reason, a silicon wafer, a gold substrate, and a fused silica substrate which are used to assess the measurement uncertainty always have non-ideal physical properties such as surface roughness and interface layer basically.
Therefore, there is a need to develop a rotating-element spectroscopic ellipsometer capable of solving the above-mentioned problems.
Korean Patent Laid-Open Publication No. 10-2013-0019495 discloses a rotating-element spectroscopic ellipsometer and a method for measuring physical properties of a sample using the same.